This review describes the surface structures (fibrils and fimbriae), on oral bacteria that can be responsible for adhesion to buccal mucosa, teeth and other bacteria (coaggregation). Fibrils and fimbriae have been found on a number of different speciesof Streptococcus, ActinomycesandBacteroides, and are morphologically and biochemically distinct from each other. Either structure can be present on different strains of the same species ofStreptococcus. Fibrils or fimbriae are present on different species ofBacteroides, andActinomycesspecies only exhibit fimbriae. The evidence for the existence of two distinct types of surface structure is evaluated. Fimbriae are flexible peritrichous structures composed of protein, with sub‐unit molecular weights varying from 43 kDa forBacteroides gingivalis381 fimbriae, to 65 kDa forActinomyces viscosusT14V fimbriae. Fimbriae are thin (3–5 nm wide) and are characterised by a definite width all along their length. Fibrils can be either peritrichous, or less commonly arranged in lateral tufts, and they have a reproducible length (<400 nm) that is strain‐dependent. Fibrils are characterised by their ability to clump in negative stain, so that individual widths cannot be measured. Fibrils are glycoprotein in nature with a sub‐unit molecular weight ranging from 220 kDa for the fibrillar host adhesion factor fromStreptococcus salivariusHB, to 320 kDa for the fibrillar veillonella binding protein, also fromS. salivariusHB. Some fibrils and fimbriae carry multiple adhesins adhering to more than one type of receptor. The evidence linking fibrils and fimbriae with adhesion to oral surfaces is assessed.